SUPPLEMENTARY IRRIGATION FOR SEQUENTIAL CROPPING IN THE ETHIOPIAN HIGHLAND VERTISOLS USING BROADBED AND FURROW LAND MANAGEMENT-SYSTEM

The productivity of the vertisols in the Ethiopian highlands is below their potential mainly due to waterlogging in the main rainy season (June-September). A two year trial (1987-1988) was conducted to assess the effect of improved drainage and supplementary irrigation on sequential wheatchickpea cropping on Vertisol. Wheat was grown during the main rainy season on broadbeds and furrows (BBF), made with an animal drawn implement (broadbed maker, BBM) to drain off the excess water. The wheat harvest was followed by planting of chickpea (Cicer arientinum, Desi type) in the beginning of the dry season. Through the furrows of the BBF-system four irrigation treatments were applied: no irrigation; irrigation at planting; irrigation at planting and at vegetative stage; irrigation at planting, vegetative stage and at 50% flowering. The results showed that if the rain stop after planting the second crop, chickpea, will not emerge without irrigation. This happened in one of the two years of experimentation. In that particular year (1987), the soil moisture in the seed zone (0-10 cm layer) was 26% and soil-water tension was 16.87 kPa (168.7 cm H2O). Irrigation at planting established the chickpea crop well and gave the highest grain yield, while three irrigations gave significantly lower (P < 0.05) grain yield than one or two irrigations.